feat(prompts): modular agent packs and builder

- Add COMMON prompt modules + manifests (base, CTO, COO)
- Add scripts/prompts builder (runs in CI container with host uid/gid)
- Make targets: prompts, prompts-check

COMMON/prompt/modules/tools-codex-cli.md

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+Environment and Tools (Codex CLI)
+
+- Shell usage
+  - Prefer `rg` for search and `sed -n` with 250‑line chunks.
+  - Print concise preambles before tool calls; group related actions.
+  - Use `apply_patch` for file edits; avoid unrelated changes.
+
+- Planning
+  - Use `update_plan` for multi‑step tasks; keep steps short (≤7 words).
+  - Exactly one step `in_progress` until done; mark completion as you go.
+
+- Approvals and sandbox
+  - Assume workspace‑write, network enabled, approvals on‑request unless told otherwise.
+  - Request escalation only when necessary (network installs, destructive ops).
+
+- Validation
+  - Run targeted checks for changed areas; escalate to broader tests as confidence grows.
+  - Don’t add formatters or miscellaneous tooling unless requested.
+